U.S. patent number 7,838,709 [Application Number 11/822,408] was granted by the patent office on 2010-11-23 for lubricating base oil and lubricating oil composition.
This patent grant is currently assigned to Nippon Oil Corporation, Petroleum Energy Center. Invention is credited to Shigeki Matsui, Shinichi Shirahama, Kazuo Tagawa, Akira Yaguchi.
United States Patent |
7,838,709 |
Matsui , et al. |
November 23, 2010 |
Lubricating base oil and lubricating oil composition
Abstract
The invention provides a lubricating base oil with a saturated
component content of 90% by mass or greater, a proportion of cyclic
saturated components of no greater than 40% by mass of the
saturated components, a viscosity index of 110 or greater, an
aniline point of 106 or greater and an .epsilon.-methylene
proportion of 14-20% of the total constituent carbons, as well as a
lubricating oil composition comprising the lubricating base
oil.
Inventors: |
Matsui; Shigeki (Yokohama,
JP), Yaguchi; Akira (Yokohama, JP), Tagawa;
Kazuo (Yokohama, JP), Shirahama; Shinichi
(Yokohama, JP) |
Assignee: |
Nippon Oil Corporation (Tokyo,
JP)
Petroleum Energy Center (Tokyo, JP)
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Family
ID: |
38950110 |
Appl.
No.: |
11/822,408 |
Filed: |
July 5, 2007 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20080015400 A1 |
Jan 17, 2008 |
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Foreign Application Priority Data
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Jul 6, 2006 [JP] |
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P2006-187074 |
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Current U.S.
Class: |
585/1; 208/40;
585/13; 585/9; 508/111; 208/33 |
Current CPC
Class: |
C10M
109/02 (20130101); C10M 101/00 (20130101); C10N
2020/01 (20200501); C10N 2020/065 (20200501); C10N
2030/74 (20200501); C10N 2030/08 (20130101); C10N
2020/02 (20130101); C10N 2020/013 (20200501); C10N
2030/06 (20130101); C10N 2070/00 (20130101) |
Current International
Class: |
C07C
7/20 (20060101); C10G 73/06 (20060101); C10L
1/16 (20060101) |
Field of
Search: |
;508/111 ;585/1,6.6,9,13
;208/33,34,40,41 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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4-036391 |
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Feb 1992 |
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JP |
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4-068082 |
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Mar 1992 |
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JP |
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4-120193 |
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Apr 1992 |
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JP |
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Primary Examiner: Caldarola; Glenn A
Assistant Examiner: Vasisth; Vishal
Attorney, Agent or Firm: Finnegan, Henderson, Farabow,
Garrett & Dunner, LLP
Claims
The invention claimed is:
1. A lubricating base oil having: a saturated component content of
95% by mass or greater, a cyclic saturated component proportion
which is measured based on ASTM D 2786-91 of no greater than 40% by
mass of the saturated component, a viscosity index of 110 to 160, a
kinematic viscosity at 100.degree. C. of 3.7 to 4.5 mm.sup.2/s, a
kinematic viscosity at 40.degree. C. of 13 to 19 mm.sup.2/s, a
solid point of -45 to -20.degree. C., an iodine number of no
greater than 2.5, a NOACK evaporation of 6 to 20% by mass, a ratio
(M.sub.A/M.sub.B) between the mass of monocyclic saturated
components (M.sub.A) and the mass of bicyclic or greater saturated
components (M.sub.B) of the cyclic saturated components of no
greater than 3, an aniline point of 106 or greater, a tertiary
carbon proportion of 6 to 12% of the total constituent carbons, an
.epsilon.-methylene proportion of 14 to 20% of the total
constituent carbons, and an aromatic content of 0.4% by mass or
greater.
2. The lubricating base oil according to claim 1, wherein bicyclic
or greater polycyclic saturated components constitute no greater
than 20% by mass of the saturated components.
3. The lubricating base oil according to claim 1, wherein an
aromatic content is no greater than 5% by mass.
4. A lubricating oil composition comprising the lubricating base
oil according to claim 1.
5. The lubricating base oil according to claim 1, wherein a
-35.degree. C. CCS viscosity of the base oil is less than 2800
mPas.
6. The lubricating base oil according to claim 1, wherein a
-35.degree. C. CCS viscosity of the base oil is less than 2000
mPas.
7. The lubricating base oil according to claim 1, wherein the base
oil is obtained by hydrocracking and/or hydroisomerization of a
stock oil comprising at least 50 vol % slack wax.
8. The lubricating base oil according to claim 1, wherein the base
oil is obtained by hydrocracking and/or hydroisomerization of a
stock oil comprising at least 50 vol % synthetic wax obtained by
gas-to-liquid process.
9. The lubricating oil composition according to claim 4, wherein a
-40.degree. C. MRV viscosity is no greater than 30,000 mPas.
10. The lubricating oil composition according to claim 4, wherein a
kinematic viscosity at 100.degree. C. is 4.5 to 21.9
mm.sup.2/s.
11. The lubricating oil composition according to claim 4, wherein a
viscosity index is 160 or greater.
12. The lubricating base oil according to claim 1, wherein the
ratio (M.sub.A/M.sub.B) is no greater than 2.
13. The lubricating base oil according to claim 12, wherein the
ratio (M.sub.A/M.sub.B) is no greater than 1.
14. The lubricating base oil according to claim 1, wherein the
aromatic content is 0.5% by mass or greater.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lubricating base oil and a
lubricating oil composition.
2. Related Background Art
In the field of lubricating oils, it has been attempted to improve
lubricating oil properties such as the viscosity-temperature
characteristic and heat and oxidation stability by addition of
additives to the lubricating base oils such as highly refined
mineral oils (for example, see Japanese Unexamined Patent
Publication HEI No. 4-36391, Japanese Unexamined Patent Publication
HEI No. 4-68082, Japanese Unexamined Patent Publication HEI No.
4-120193).
SUMMARY OF THE INVENTION
However, with ever increasing demands on the properties of
lubricating oils in recent times, it cannot be said that the
lubricating base oils described in the aforementioned patent
documents are always satisfactory in terms of viscosity-temperature
characteristic and heat and oxidation stability. In particular,
with SAE10 class lubricating base oils and lubricating oil
compositions containing them as major components it is difficult to
achieve both a high viscosity index and a superior level of low
temperature viscosity (CCS viscosity, MRV viscosity, Brookfield
(BF) viscosity, etc.) at -35.degree. C. and below, and they must
therefore be used in combination of lubricating base oils that
exhibit excellent low temperature viscosity such as synthetic base
oils like poly-.alpha.-olefins or esters and low-viscosity mineral
base oils. However, such synthetic oils are expensive, while
low-viscosity mineral base oils generally have low viscosity
indexes and high NOACK evaporation, and therefore addition of such
lubricating base oils increases the lubricating oil manufacturing
cost and makes it difficult to achieve a high viscosity index and
low evaporation. Furthermore, there have been limits to the
improvement in the properties by the use of such conventional
lubricating base oils and additives in combination.
The present invention has been accomplished in light of these
circumstances, and its object is to provide a lubricating base oil,
and a lubricating oil composition comprising the lubricating base
oil, which exhibit excellent viscosity-temperature characteristics
and heat and oxidation stability, and which can exhibit a high
viscosity index and low temperature viscosity properties at
-35.degree. C. and below without using synthetic oils such as
poly-.alpha.-olefins or esters or low-viscosity mineral base oils,
and especially which allow notable improvement in the MRV viscosity
of lubricating oils at -40.degree. C.
In order to solve the problems described above, the invention
provides a lubricating base oil with a saturated component content
of 95% by mass or greater, a cyclic saturated component proportion
of no greater than 40% by mass of the saturated components, a
viscosity index of 110 or greater, an aniline point of 106 or
greater, and an .epsilon.-methylene proportion of 14-20% of the
total constituent carbons.
If the saturated component content, the proportion of cyclic
saturated components in the saturated components, the viscosity
index, the aniline point and the proportion of .epsilon.-methylene
of the total constituent carbons (this will hereinafter also be
referred to simply as ".epsilon.-methylene proportion") in the
lubricating base oil of the invention satisfy the conditions
described above, it is possible to achieve an excellent
viscosity-temperature characteristic and heat and oxidation
stability. With the lubricating base oil of the invention it is
possible to achieve both a high viscosity index of 130 or higher
and a low temperature viscosity at -35.degree. C. and below, and in
particular it is possible to notably reduce the MRV viscosity at
-40.degree. C. Moreover, when additives have been added to the
lubricating base oil, an even higher level of function can be
exhibited by the additives while maintaining satisfactorily stable
dissolution of the additives in the lubricating base oil.
The lubricating base oil of the invention can also lower the
viscous resistance and stirring resistance in a practical
temperature range due to the aforementioned excellent
viscosity-temperature characteristic, and thereby maximize the
effect obtained by addition of friction modifiers and the like.
Thus, the lubricating base oil of the invention reduces energy loss
in devices in which the lubricating base oil is used, and is
therefore extremely useful for achieving energy savings.
The invention further provides a lubricating oil composition
comprising the aforementioned lubricating base oil of the
invention.
The lubricating oil composition of the invention comprises a
lubricating base oil according to the invention and therefore
exhibits a high level for both the viscosity-temperature
characteristic and heat and oxidation stability, while exhibiting a
high viscosity index and a low temperature viscosity property at
-35.degree. C. and below without using synthetic oils such as
poly-.alpha.-olefins, esters and low-viscosity mineral base oils,
and in particular it allows notable improvement in the MRV
viscosity of lubricating oils at -40.degree. C.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the invention will now be described in
detail.
The lubricating base oil of the invention is a lubricating base oil
with a saturated component content of 90% by mass or greater, a
proportion of cyclic saturated components of no greater than 40% by
mass of the saturated components, a viscosity index of 110 or
greater, an aniline point of 106 or greater and an
.epsilon.-methylene proportion of 14-20% of the total constituent
carbons.
The lubricating base oil of the invention is not particularly
restricted so long as the saturated component content, the
proportion of cyclic saturated components in the saturated
components, the viscosity index, the aniline point and the
.epsilon.-methylene proportion in the lubricating base oil of the
invention satisfy the conditions described above. Specifically,
there may be paraffinic mineral oils prepared by subjecting
lube-oil distillates obtained by atmospheric distillation and/or
vacuum distillation of crude oil to refining involving one or a
combination of refining treatments such as solvent deasphalting,
solvent extraction, hydrocracking, solvent dewaxing, catalytic
dewaxing, hydrorefining, sulfuric acid treatment and white clay
treatment, or normal paraffin base oils or isoparaffin base oils,
which satisfy the conditions described above for the saturated
component content, the proportion of cyclic saturated components in
the saturated components, the viscosity index, the aniline point
and the .epsilon.-methylene proportion in the lubricating base oil.
Such lubricating base oils may be used alone, or a combination of
two or more thereof may be used.
As preferred examples of lubricating base oils according to the
invention there may be mentioned base oils obtained by using the
following base oils (1)-(8) as feed stock oils, carrying out
prescribed refining processes to refine the feed stock oils and/or
lube-oil distillates recovered from the feed stock oils, and
recovering the lube-oil distillates. (1) Distilled oil from
atmospheric distillation of paraffinic crude oil and/or mixed-base
crude oil. (2) Distilled oil obtained by vacuum distillation of the
residue from atmospheric distillation of paraffinic crude oil
and/or mixed-base crude oil (WVGO). (3) Wax obtained by a
lubricating oil dewaxing step (slack wax or the like) and/or
synthetic wax obtained by a gas-to-liquid (GTL) process
(Fischer-Tropsch wax, GTL wax or the like). (4) Blended oil
comprising one or more selected from among base oils (1)-(3) and/or
mildly hydrocracked oil obtained from the blended oil. (5) Blended
oil comprising two or more selected from among base oils (1)-(4).
(6) Deasphalted oil (DAO) from base oil (1), (2), (3), (4) or (5).
(7) Mildly hydrocracked oil (MHC) obtained from base oil (6). (8)
Blended oil comprising two or more selected from base oils
(1)-(7).
The prescribed refining process described above is preferably
hydrorefining such as hydrocracking or hydrofinishing; solvent
refining such as furfural solvent extraction; dewaxing such as
solvent dewaxing or catalytic dewaxing; white clay refining with
acidic white clay or active white clay, or chemical (acid or
alkali) washing such as sulfuric acid treatment or caustic soda
washing. According to the invention, any one of these refining
processes may be used alone, or a combination of two or more
thereof may be used in combination. When a combination of two or
more refining processes is used, the order is not particularly
restricted and may be selected as appropriate.
The lubricating base oil of the invention is most preferably one of
the following base oils (9) or (10) obtained by the prescribed
treatment of a base oil selected from among base oils (1)-(8) above
or a lube-oil distillate recovered from the base oil. (9)
Hydrocracked mineral oil obtained by hydrocracking of a base oil
selected from among base oils (1)-(8) above or a lube-oil
distillate recovered from the base oil, dewaxing treatment such as
solvent dewaxing or catalytic dewaxing of the product or a lube-oil
distillate recovered from distillation of the product, or further
distillation after the dewaxing treatment. (10) Hydroisomerized
mineral oil obtained by hydroisomerization of a base oil selected
from among base oils (1)-(8) above or a lube-oil distillate
recovered from the base oil, and dewaxing treatment such as solvent
dewaxing or catalytic dewaxing of the product or a lube-oil
distillate recovered from distillation of the product, or further
distillation after the dewaxing treatment.
In obtaining the lubricating base oil of (9) or (10) above, a
solvent refining treatment and/or hydrofinishing treatment step may
also be carried out in a convenient manner if necessary.
There are no particular restrictions on the catalyst used for the
hydrocracking and hydroisomerization, but there may be suitably
used hydrocracking catalysts comprising a hydrogenating metal (for
example, one or more metals of Group Via or metals of Group VIII of
the Periodic Table) loaded on a carrier which is a complex oxide
with decomposing activity (for example, silica-alumina,
alumina-boria, silica-zirconia or the like) or a combination of two
or more of such complex oxides bound with a binder, or
hydroisomerization catalysts obtained by loading one or more metals
of Group VIII having hydrogenating activity on a carrier comprising
zeolite (for example, ZSM-5, zeolite beta, SAPO-11 or the like).
The hydrocracking catalyst or hydroisomerization catalyst may be
used as a combination of layers or a mixture.
The reaction conditions for hydrocracking and hydroisomerization
are not particularly restricted, but preferably the hydrogen
partial pressure is 0.1-20 MPa, the mean reaction temperature is
150-450.degree. C., the LHSV is 0.1-3.0 hr.sup.-1 and the
hydrogen/oil ratio is 50-20,000 scf/bbl.
The following production process A may be mentioned as a preferred
example of a production process for the lubricating base oil of the
invention.
Specifically, production process A according to the invention
comprises
a first step of preparing a hydrocracking catalyst comprising a
carrier having an NH.sub.3 desorption percentage at 300-800.degree.
C. of no greater than 80% with respect to the total NH.sub.3
desorption, based on NH.sub.3 desorption temperature dependence
evaluation, and at least one metal from among metals of Group Via
and at least one metal from among metals of Group VIII of the
Periodic Table supported on the carrier,
a second step of hydrocracking of a feed stock oil comprising at
least 50 vol % slack wax in the presence of a hydrocracking
catalyst, at a hydrogen partial pressure of 0.1-14 MPa, a mean
reaction temperature of 230-430.degree. C., an LHSV of 0.3-3.0
hr.sup.-1 and a hydrogen/oil ratio of 50-14,000 scf/bbl,
a third step of distilling separation of the cracked product oil
obtained in second step to obtain a lube-oil distillate, and
a fourth step of dewaxing treatment of the lube-oil distillate
obtained in third step.
Production process A will now be explained in detail.
(Feed Stock Oil)
For production process A, a stock oil comprising at least 50 vol %
slack wax is used. The phrase "stock oil comprising at least 50 vol
% slack wax" according to the invention refers to both feed stock
oils composed entirely of slack wax, and stock oil that is a
blended oil of slack wax and another stock oil and comprises at
least 50 vol % slack wax.
Slack wax is the wax-containing component as a by-product of the
solvent dewaxing step during production of a lubricating base oil
from a paraffinic lube-oil distillate, and according to the
invention the term includes slack wax obtained by further
subjecting the wax-containing component to deoiling treatment. The
major components of slack wax are n-paraffins and branched
paraffins with few side chains (isoparaffins), and the naphthene
and aromatic component contents are low. The kinematic viscosity of
the slack wax used for preparation of the stock oil may be selected
as appropriate for the kinematic viscosity of the lubricating base
oil to be obtained, but for production of a low-viscosity base oil
as a lubricating base oil for the invention, a relatively low
viscosity slack wax is preferred, with a 100.degree. C. kinematic
viscosity of about 2-25 mm.sup.2/s, preferably 2.5-20 mm.sup.2/s
and more preferably 3-15 mm.sup.2/s.
The other properties of the slack wax may be as desired, although
the melting point is preferably 35-80.degree. C., more preferably
45-70.degree. C. and even more preferably 50-60.degree. C. The oil
content of the slack wax is preferably no greater than 60% by mass,
more preferably no greater than 50% by mass, even more preferably
no greater than 25% by mass and most preferably no greater than 10%
by mass, while also preferably 0.5% by mass or greater and more
preferably 1% by mass or greater. The sulfur content of the slack
wax is preferably no greater than 1% by mass and more preferably no
greater than 0.5% by mass, while also preferably 0.001% by mass or
greater.
The oil content of the thoroughly deoiled slack wax (hereinafter
referred to as "slack wax A") is preferably 0.5-10% by mass and
more preferably 1-8% by mass. The sulfur content of slack wax A is
preferably 0.001-0.2% by mass, more preferably 0.01-0.15% by mass
and even more preferably 0.05-0.12% by mass. However, the oil
content of slack wax that has either not been subjected to deoiling
treatment or has been subjected only to insufficient deoiling
treatment (hereinafter, "slack wax B") is preferably 10-60% by
mass, more preferably 12-50% by mass and even more preferably
15-25% by mass. The sulfur content of slack wax B is preferably
0.05-1% by mass, more preferably 0.1-0.5% by mass and even more
preferably 0.15-0.25% by mass. These slack waxes A and B may be
desulfurized depending on the type and properties of the
hydrocracking/isomerization catalyst, in which case the sulfur
content is preferably no greater than 0.01% by mass and more
preferably no greater than 0.001% by mass.
The invention is highly useful as it allows high added-value
lubricating base oils with high viscosity indexes as well as
excellent low-temperature characteristics and heat and oxidation
stability, to be obtained even when the feed stock oils used are
relatively crude and cheap slack waxes with relatively high oil and
sulfur contents.
When the stock oil is a blended oil comprising a slack wax and
another stock oil, the other stock oil is not particularly
restricted so long as it has a slack wax content of 50 vol % or
greater of the total blended oil, but preferably a blended oil
comprising a heavy atmospheric distilled oil and/or a vacuum
distilled oil from crude oil is used.
When the stock oil is a blended oil comprising slack wax and
another stock oil, the proportion of slack wax in the total blended
oil is preferably at least 70 vol % and more preferably at least 75
vol %, from the standpoint of producing a base oil with a high
viscosity index. If the proportion is less than 50 vol %, the oil
components such as aromatic and naphthene components will be
increased in the obtained lubricating base oil, and the viscosity
index of the lubricating base oil will tend to be reduced.
On the other hand, the heavy atmospheric distilled oil and/or
vacuum distilled oil from crude oil which is used with the slack
wax is preferably a fraction with a run-off of at least 60 vol % in
a distillation temperature range of 300-570.degree. C., in order to
maintain a high viscosity index for the lubricating base oil
product.
(Hydrocracking Catalyst)
The hydrocracking catalyst used in production process A described
above comprises at least one metal from among metals of Group VIa
and at least one metal from among metals of Group VIII of the
Periodic Table, supported on a carrier with an NH.sub.3 desorption
percentage at 300-800.degree. C. of no greater than 80% with
respect to the total NH.sub.3 desorption, based on NH.sub.3
desorption temperature dependence evaluation.
The "NH.sub.3 desorption temperature dependence evaluation"
referred to here is the method described in the literature (Sawa
M., Niwa M., Murakami Y, Zeolites 1990, 10, 532; Karge H. G.,
Dondur V, J. Phys. Chem. 1990, 94, 765 and elsewhere), and it is
carried out as follows. First, the catalyst carrier is pretreated
under a nitrogen stream for at least 30 minutes at a temperature of
400.degree. C. or higher to remove the adsorbed molecules, and then
adsorption is carried out at 100.degree. C. until neutralization of
the NH.sub.3. Next, the temperature of the catalyst carrier is
raised to 100-800.degree. C. at a temperature-elevating rate of no
more than 10.degree. C./min for NH.sub.3 desorption, and the
NH.sub.3 separated by desorption is monitored at each prescribed
temperature. The desorption percentage of NH.sub.3 at 300.degree.
C.-800.degree. C. with respect to the total NH.sub.3 desorption
(desorption at 100-800.degree. C.) is then calculated.
The catalyst carrier used for production process A has an NH.sub.3
desorption percentage at 300-800.degree. C. of no greater than 80%
with respect to the total NH.sub.3 desorption based on NH.sub.3
desorption temperature dependence evaluation, and it is preferably
no greater than 70% and more preferably no greater than 60%. By
using such a carrier to construct the hydrocracking catalyst,
acidic substances that govern the cracking activity are
sufficiently inhibited, so that it is possible to efficiently and
reliably produce isoparaffins by decomposing isomerization of
high-molecular-weight n-paraffins that derive from the slack wax in
the stock oil by hydrocracking, and to satisfactorily inhibit
excess cracking of the produced isoparaffin compounds. As a result,
it is possible to obtain a sufficient amount of molecules with a
high viscosity index having a suitably branched chemical structure,
within a suitable molecular weight range.
As such carriers there are preferred two-element oxides which are
amorphous and acidic, and as examples there may be mentioned the
two-element oxides cited in the literature (for example, "Metal
Oxides and Their Catalytic Functions", Shimizu, T., Kodansha,
1978).
Preferred among these are amorphous complex oxides that contain
acidic two-element oxides obtained as complexes of two oxides of
elements selected from among Al, B, Ba, Bi, Cd, Ga, La, Mg, Si, Ti,
W, Y, Zn and Zr. The proportion of each oxide in such acidic
two-element oxides can be adjusted to obtain an acidic carrier
suitable for the purpose in the aforementioned NH.sub.3
adsorption/desorption evaluation. The acidic two-element oxide
composing the carrier may be any one of the above, or a mixture of
two or more thereof. The carrier may also be composed of the
aforementioned acidic two-element oxide, or it may be a carrier
obtained by binding the acidic two-element oxide with a binder.
The carrier is preferably one containing at least one acidic
two-element oxide selected from among amorphous silica-alumina,
amorphous silica-zirconia, amorphous silica-magnesia, amorphous
silica-titania, amorphous silica-boria, amorphous alumina-zirconia,
amorphous alumina-magnesia, amorphous alumina-titania, amorphous
alumina-boria, amorphous zirconia-magnesia, amorphous
zirconia-titania, amorphous zirconia-boria, amorphous
magnesia-titania, amorphous magnesia-boria and amorphous
titania-boria. The acidic two-element oxide composing the carrier
may be any one of the above, or a mixture of two or more thereof.
The carrier may also be composed of the aforementioned acidic
two-element oxide, or it may be a carrier obtained by binding the
acidic two-element oxide with a binder. The binder is not
particularly restricted so long as it is one commonly used for
catalyst preparation, but those selected from among silica,
alumina, magnesia, titania, zirconia and clay, or mixtures thereof,
are preferred.
For production process A, the hydrocracking catalyst has a
structure wherein at least one metal of Group VIa of the Periodic
Table (molybdenum, chromium, tungsten or the like) and at least one
metal of Group VIII (nickel, cobalt, palladium, platinum or the
like) are loaded on the aforementioned carrier. These metals have a
hydrogenating function, and on the acidic carrier they complete a
reaction which causes cracking or branching of the paraffin
compound, thus performing an important role for production of
isoparaffins with a suitable molecular weight and branching
structure.
As regards the loading amounts of the metals in the hydrocracking
catalyst, the loading amount of metals of Group VIa is preferably
5-30% by mass for each metal, and the loading amount of metals of
Group VIII is preferably 0.2-10% by mass for each metal.
The hydrocracking catalyst used for production process A more
preferably comprises molybdenum in a range of 5-30% by mass as the
one or more metals of Group Via, and nickel in a range of 0.2-10%
by mass as the one or more metals of Group VIII.
The hydrocracking catalyst composed of the carrier, at least one
metal of Group VIa and at least one metal of Group VIII is
preferably used in a sulfurized state for hydrocracking. The
sulfurizing treatment may be carried out by a publicly known
method.
(Hydrocracking Step)
For production process A, the stock oil containing at least 50 vol
% slack wax is hydrocracked in the presence of the hydrocracking
catalyst, at a hydrogen partial pressure of 0.1-14 MPa, preferably
1-14 MPa and more preferably 2-7 MPa; a mean reaction temperature
of 230-430.degree. C., preferably 330-400.degree. C. and more
preferably 350-390.degree. C.; an LHSV of 0.3-3.0 hr.sup.-1 and
preferably 0.5-2.0 hr.sup.-1 and a hydrogen/oil ratio of 50-14,000
scf/bbl and preferably 100-5000 scf/bbl.
In the hydrocracking step, the n-paraffins derived from the slack
wax in the stock oil are isomerized to isoparaffins during
cracking, producing isoparaffin components with a low pour point
and a high viscosity index, but it is possible to simultaneously
decompose the aromatic compounds in the stock oil, which disturb
increasing the viscosity index, to monocyclic aromatic compounds,
naphthene compounds and paraffin compounds, and to decompose the
polycyclic naphthene compounds which disturb increasing viscosity
index to monocyclic naphthene compounds or paraffin compounds. From
the viewpoint of increasing the viscosity index, it is preferred to
minimize the high boiling point and low viscosity index compounds
in the stock oil.
If the cracking severity as an evaluation of the extent of reaction
is defined by the following formula: (cracking severity (vol
%))=100-(proportion (vol %) of fraction with boiling point of
360.degree. C. or higher in product) then the cracking severity is
preferably 3-90 vol %. A cracking severity of less than 3 vol % is
not preferred because it will result in insufficient production of
isoparaffins by decomposing isomerization of high-molecular-weight
n-paraffins with a high pour point in the stock oil and
insufficient hydrocracking of the aromatic or polycyclic naphthene
components with an inferior viscosity index, while a cracking
severity of greater than 90 vol % is not preferred because it will
reduce the lube-oil distillate yield.
(Distilling Separation Step)
The lube-oil distillate is then subjected to distilling separation
from the cracked product oil obtained from the hydrocracking step
described above. A fuel oil fraction is also sometimes obtained as
the light fraction.
The fuel oil fraction is the fraction obtained as a result of
thorough desulfurization and denitrogenization, and thorough
hydrogenation of the aromatic components. The naphtha fraction with
a high isoparaffin content, the kerosene fraction with a high smoke
point and the gas oil fraction with a high cetane number are all
high quality products suitable as fuel oils.
On the other hand, even with insufficient hydrocracking of the
lube-oil distillate, a portion thereof may be supplied for repeat
of the hydrocracking step. In order to obtain a lube-oil distillate
with the desired kinematic viscosity, the lube-oil distillate may
then be subjected to vacuum distillation. The vacuum distillation
separation may be carried out after the dewaxing treatment
described below.
In the evaporating separation step, the cracked product oil
obtained from the hydrocracking step may be subjected to vacuum
distillation to satisfactorily obtain a lubricating base oil such
as 70 Pale, SAE10 and SAE20.
A system using a lower viscosity slack wax as the stock oil is
suitable for producing an increased 70 Pale or SAE10 fraction,
while a system using a high viscosity slack wax in the range
mentioned above as the stock oil is suitable for obtaining more
SAE20. However even with high viscosity slack wax, conditions for
producing significant amounts of 70 Pale and SAE10 may be selected
depending on the extent of the cracking reaction.
(Dewaxing Step)
The lube-oil distillate obtained by fractional distillation from
the cracked product oil in the distilling separation step has a
high pour point, and therefore dewaxing is carried out to obtain a
lubricating base oil with the desired solid point. The dewaxing
treatment may be carried out by an ordinary method such as a
solvent dewaxing method or catalytic dewaxing method. Solvent
dewaxing methods generally employ MEK and toluene mixed solvents,
but solvents such as benzene, acetone or MIBK may also be used. In
order to improve the low temperature viscosity property of the
dewaxing oil from the obtained SAE10 class fraction, the
solvent/oil ratio is preferably 1-6, and the filtration temperature
is preferably no higher than -25.degree. C., more preferably -26 to
-45.degree. C., even more preferably -27 to -40.degree. C. and most
preferably -28 to -35.degree. C. The wax removed by filtration may
be supplied again as slack wax to a hydrocracking step.
The production process described above may also include solvent
refining treatment and/or hydrorefining treatment in addition to
the dewaxing treatment. Such additional treatment is performed to
improve the ultraviolet stability or oxidation stability of the
lubricating base oil, and may be carried out by methods ordinarily
used for lubricating oil refining steps.
The solvent used for solvent refining will usually be furfural,
phenol, N-methylpyrrolidone or the like, in order to remove the
small amounts of aromatic compounds and especially polycyclic
aromatic compounds, remaining in the lube-oil distillate.
The hydrorefining is carried out for hydrogenation of the olefin
compounds and aromatic compounds, and the catalyst therefor is not
particularly restricted; there may be used alumina catalysts
supporting at least one metal from among Group VIa metals such as
molybdenum and at least one metal from among Group VIII metals such
as cobalt and nickel, under conditions with a reaction pressure
(hydrogen partial pressure) of 7-16 MPa, a mean reaction
temperature of 300-390.degree. C. and an LHSV of 0.5-4.0
hr.sup.-1.
The following production process B may be mentioned as another
preferred example of a production process for the lubricating base
oil of the invention.
Specifically, production process B according to the invention
comprises
a fifth step of hydrocracking and/or hydroisomerization of a stock
oil containing paraffinic hydrocarbons in the presence of a
catalyst, and
a sixth step of dewaxing treatment of the product obtained from the
fifth step or of the lube-oil distillate collected by distillation
or the like from the product.
Production process B will now be explained in detail.
(Stock Oil)
For production process B there is used a stock oil containing
paraffinic hydrocarbons. The term "paraffinic hydrocarbons"
according to the invention refers to hydrocarbons with a paraffin
molecule content of 70% by mass or greater. The number of carbons
of the paraffinic hydrocarbons is not particularly restricted but
will normally be about 10-100. The method for producing the
paraffinic hydrocarbons is not particularly restricted, and various
petroleum-based and synthetic paraffinic hydrocarbons may be used,
but as especially preferred paraffinic hydrocarbons there may be
mentioned synthetic waxes (Fischer-Tropsch wax (FT wax), GTL wax,
etc.) obtained by gas-to-liquid (GTL) processes, among which FT wax
is preferred. Synthetic wax is preferably wax composed mainly of
normal paraffins with 15-80 and more preferably 20-50 carbon
atoms.
The kinematic viscosity of the paraffinic hydrocarbons used for
preparation of the stock oil may be appropriately selected
according to the desired kinematic viscosity of the lubricating
base oil, but for production of a low-viscosity base oil as a
lubricating base oil of the invention, relatively low viscosity
paraffinic hydrocarbons with a 100.degree. C. kinematic viscosity
of about 2-25 mm.sup.2/s, preferably about 2.5-20 mm.sup.2/s and
more preferably about 3-15, are preferred. The other properties of
the paraffinic hydrocarbons may be as desired, but when the
paraffinic hydrocarbons are synthetic wax such as FT wax, the
melting point is preferably 35-80.degree. C., more preferably
50-80.degree. C. and even more preferably 60-80.degree. C. The oil
content of the synthetic wax is preferably no greater than 10% by
mass, more preferably no greater than 5% by mass and even more
preferably no greater than 2% by mass. The sulfur content of the
synthetic wax is preferably no greater than 0.01% by mass, more
preferably no greater than 0.001% by mass and even more preferably
no greater than 0.0001% by mass.
When the stock oil is a blended oil comprising the aforementioned
synthetic wax and another stock oil, the other stock oil is not
particularly restricted so long as it has a synthetic wax
proportion of at least 50 vol % of the total blended oil, but it is
preferably a blended oil comprising a heavy atmospheric distilled
oil and/or a vacuum distilled oil from crude oil.
When the stock oil is a blended oil comprising the synthetic wax
and another stock oil, the proportion of synthetic wax of the total
blended oil is preferably at least 70 vol % and more preferably at
least 75 vol %, from the standpoint of producing a base oil with a
high viscosity index. If the proportion is less than 70 vol %, the
oil components such as aromatic and naphthene components will be
increased in the obtained lubricating base oil, and the viscosity
index of the lubricating base oil will tend to be reduced.
On the other hand, the heavy atmospheric distilled oil and/or
vacuum distilled oil from crude oil which is used with the
synthetic wax is preferably a fraction with a run-off of at least
60 vol % in a distillation temperature range of 300-570.degree. C.,
in order to maintain a high viscosity index for the lubricating
base oil product.
(Catalyst)
There are no particular restrictions on the catalyst used for
production process B, but it is preferably a catalyst comprising at
least one metal selected from metals of Group VIb and Group VIII of
the Periodic Table as an active metal component supported on a
carrier containing an aluminosilicate.
An aluminosilicate is a metal oxide composed of the three elements
aluminum, silicon and oxygen. Other metal elements may also be
included in ranges that do not interfere with the effect of the
invention. In this case, the amount of other metal elements is
preferably no greater than 5% by mass and more preferably no
greater than 3% by mass of the total of alumina and silica in terms
of their oxides. As examples of metal elements that may be included
there may be mentioned titanium, lanthanum and manganese.
The crystallinity of the aluminosilicate can be estimated by the
proportion of tetracoordinated aluminum atoms among the total
aluminum atoms, and the proportion can be measured by .sup.27Al
solid NMR. The aluminosilicate used for the invention has a
tetracoordinated aluminum proportion of preferably at least 50% by
mass, more preferably at least 70% by mass and even more preferably
at least 80% by mass of the total aluminum. Aluminosilicates with
tetracoordinated aluminum contents of greater than 50% by mass of
the total aluminum are known as "crystalline aluminosilicates".
Zeolite may be used as a crystalline aluminosilicate. As preferred
examples there may be mentioned Y-zeolite, ultrastabilized
Y-zeolite (USY zeolite), .beta.-zeolite, mordenite and ZSM-5, among
which USY zeolite is particularly preferred. According to the
invention, one type of crystalline aluminosilicate may be used
alone, or two or more may be used in combination.
The method of preparing the carrier containing the crystalline
aluminosilicate may be a method in which a mixture of the
crystalline aluminosilicate and binder is shaped and the shaped
body is calcinated. There are no particular restrictions on the
binder used, but alumina, silica, silica-alumina, titania and
magnesia are preferred, and alumina is particularly preferred.
There are also no particular restrictions on the proportion of
binder used, but normally it will be preferably 5-99% by mass and
more preferably 20-99% by mass based on the total mass of the
shaped body. The calcinated temperature for the shaped body
comprising the crystalline aluminosilicate and binder is preferably
430-470.degree. C., more preferably 440-460.degree. C. and even
more preferably 445-455.degree. C. The calcinating time is not
particularly restricted but will normally be 1 minute-24 hours,
preferably 10 minutes to 20 hours and more preferably 30 minutes-10
hours. The calcinating may be carried out in an air atmosphere, but
is preferably carried out in an oxygen-free atmosphere such as a
nitrogen atmosphere.
The Group VIb metal supported on the carrier may be chromium,
molybdenum, tungsten or the like, and the Group VIII metal may be,
specifically, cobalt, nickel, rhodium, palladium, iridium, platinum
or the like. These metals may be used as single metals alone, or
two or more thereof may be used in combination. For a combination
of two or more metals, two precious metals such as platinum and
palladium may be combined, two base metals such as nickel, cobalt,
tungsten and molybdenum may be combined, or a precious metal and a
base metal may be combined.
The metal may be loaded onto the carrier by impregnation of the
carrier with a solution containing the metal, or by a usual method
such as ion exchange. The loading amount of the metal may be
selected as appropriate, but it will usually be 0.05-2% by mass and
preferably 0.1-1% by mass based on the total mass of the
catalyst.
(Hydrocracking/Hydroisomerization Step)
Production process B includes hydrocracking/hydroisomerization of a
stock oil containing paraffinic hydrocarbons, in the presence of
the aforementioned catalyst. The hydrocracking/hydroisomerization
step may be carried out using a fixed bed reactor. The conditions
for the hydrocracking/hydroisomerization are preferably, for
example, a temperature of 250-400.degree. C., a hydrogen pressure
of 0.5-10 MPa and a stock oil liquid space velocity (LHSV) of
0.5-10 h.sup.-1.
(Distilling Separation Step)
The lube-oil distillate is then subjected to distilling separation
from the cracked product oil obtained from the
hydrocracking/hydroisomerization step described above. The
distilling separation step in production process B is the same as
the distilling separation step in production process A and will not
be explained again here.
(Dewaxing Step)
The lube-oil distillate obtained by fractional distillation from
the cracked product oil in the distilling separation step described
above is then subjected to dewaxing. The dewaxing step may be
carried out by a conventionally known dewaxing process such as
solvent dewaxing or catalytic dewaxing. When the substances with a
boiling point of 370.degree. C. and below in the
cracking/isomerization product oil have not been separated from the
high boiling point substances before dewaxing, the entire
hydroisomerization product may be dewaxed, or the fraction with a
boiling point of above 370.degree. C. may be dewaxed, depending on
the intended purpose of the cracking/isomerization product oil.
For solvent dewaxing, the hydroisomerization product is contacted
with cool ketone and acetone and another solvent such as MEK or
MIBK, and then cooled for precipitation of the high pour point
substances as solid wax, and the precipitate separated from the
solvent-containing lube-oil distillate (raffinate). The raffinate
is then cooled with a scraped surface chiller for removal of the
solid wax. Low molecular hydrocarbons such as propane can also be
used for the dewaxing, in which case the cracking/isomerization
product oil and low molecular hydrocarbons are mixed and at least a
portion thereof is gasified to further cool the
cracking/isomerization product oil and precipitate the wax. The wax
is separated from the raffinate by filtration, membrane separation
or centrifugal separation. The solvent is then removed from the
raffinate and the raffinate is subjected to fractional distillation
to obtain the target lubricating base oil.
In the case of catalytic dewaxing (catalyst dewaxing), the
cracking/isomerization product oil is reacted with hydrogen in the
presence of a suitable dewaxing catalyst under conditions effective
for lowering the pour point. For catalytic dewaxing, some of the
high-boiling-point substances in the cracking/isomerization product
are converted to low-boiling-point substances, and then the
low-boiling-point substances are separated from the heavy base oil
fraction and the base oil fraction is subjected to fractional
distillation to obtain two or more lubricating base oils. The
low-boiling-point substances may be separated either before
obtaining the target lubricating base oil or during the fractional
distillation.
The dewaxing catalyst is not particularly restricted so long as the
solid point of the dewaxing oil from the SAE10 class fraction is
-25.degree. C. or below, it is preferably one that yields the
target lubricating base oil at high yield from the
cracking/isomerization product oil. As such dewaxing catalysts
there are preferred shape-selective molecular sieves, and
specifically there may be mentioned ferrierite, mordenite, ZSM-5,
ZSM-11, ZSM-23, ZSM-35, ZSM-22 (also known as Theta-1 or TON),
silicoaluminophosphates (SAPO) and the like. These molecular sieves
are preferably used in combination with catalyst metal components
and more preferably in combination with precious metals. An example
of a preferred combination is a complex of platinum and
H-mordenite.
The dewaxing conditions are not particularly restricted, but the
temperature is preferably 200-500.degree. C. and the hydrogen
pressure is preferably 10-200 bar (1 MPa-20 MPa). For a
flow-through reactor, the H.sub.2 treatment speed is preferably
0.1-10 kg/l/hr and the LHSV is preferably 0.1-10.sup.-1 and more
preferably 0.2-2.0 h.sup.-1. The dewaxing is preferably carried out
in such a manner that substances with initial boiling points of
350-400.degree. C., normally present at no greater than 40% by mass
and preferably no greater than 30% by mass in the
cracking/isomerization product oil, are converted to substances
with boiling points of below their initial boiling points.
Production process A and production process B were explained above
as preferred production processes for lubricating base oils of the
invention, but the production process for a lubricating base oil of
the invention is not limited thereto. For example, in production
process A, a synthetic wax such as FT wax or GTL wax may be used
instead of slack wax. Also, a stock oil comprising slack wax
(preferably slack wax A or B) may be used in production process B.
In addition, production processes A and B may employ both slack wax
(preferably slack wax A or B) and synthetic wax (preferably FT wax
or GTL wax).
When the stock oil used for production of the lubricating base oil
of the invention is a blended oil comprising the aforementioned
slack wax and/or synthetic wax and a stock oil in addition to these
waxes, the content of the slack wax and/or synthetic wax is
preferably at least 50% by mass based on the total mass of the
stock oil.
The stock oil for production of the lubricating base oil of the
invention is preferably a stock oil comprising slack wax and/or
synthetic wax wherein the oil content is preferably no greater than
60% by mass, more preferably no greater than 50% by mass and even
more preferably no greater than 25% by mass.
The lubricating base oil of the invention will now be explained in
greater detail.
The saturated component content of the lubricating base oil of the
invention is 90% by mass as mentioned above, preferably 95% by mass
or greater, more preferably 97% by mass or greater and even more
preferably 98% by mass or greater, based on the total mass of the
lubricating base oil. The proportion of cyclic saturated components
in the saturated components is 40% by mass as mentioned above, but
it is preferably no greater than 30% by mass, more preferably no
greater than 25% by mass, even more preferably no greater than 20%
by mass, yet more preferably no greater than 10% by mass and most
preferably no greater than 5% by mass. If the saturated component
content and the proportion of cyclic saturated components in the
saturated components satisfies the conditions specified above, and
the viscosity index, aniline point and .epsilon.-methylene
proportion also satisfy the specified conditions, it will be
possible to achieve a satisfactory viscosity-temperature
characteristic and heat and oxidation stability, and to achieve
both a high viscosity index and an excellent low temperature
viscosity property at below -35.degree. C., even without using
synthetic oils such as poly-.alpha.-olefins or esters or
low-viscosity mineral oil base oils. Moreover, when additives have
been added to the lubricating base oil, it can exhibit an even
higher level of function for the additives while maintaining
satisfactorily stable dissolution of the additives in the
lubricating base oil. In addition, if the saturated component
content and the proportion of cyclic saturated components among the
saturated components satisfy these conditions, it will be possible
to improve the frictional properties of the lubricating base oil
itself, thereby achieving an improved effect of reducing friction
and providing greater energy savings.
If the saturated component content is less than 90% by mass, the
heat and oxidation stability, viscosity-temperature characteristic
and frictional properties will be inadequate. If the proportion of
cyclic saturated components among the saturated components exceeds
40% by mass, the efficacy of additives will be reduced when
additives are included in the lubricating base oil.
A cyclic saturated component content of no greater than 40% by mass
among the saturated components in the lubricating base oil of the
invention is equivalent to an acyclic saturated component content
of 60% by mass or greater among the saturated components. Acyclic
saturated components include both straight-chain paraffins and
branched paraffins. The proportion of each type of paraffin in the
lubricating base oil of the invention is not particularly
restricted, but the proportion of branched paraffins is preferably
54-99.9% by mass, more preferably 80-99.5% by mass, even more
preferably 95-99% by mass and most preferably 97-99% by mass based
on the total mass of the lubricating base oil. If the proportion of
branched paraffins in the lubricating base oil satisfies this
condition, the heat and oxidation stability and
viscosity-temperature characteristic can be further improved, and
when additives are added to the lubricating base oil, the functions
of the additives can be exhibited at an even higher level while
sufficiently maintaining stable dissolution of the additives.
The content of monocyclic saturated components and bicyclic or
greater saturated components among the saturated components in the
lubricating base oil of the invention is not particularly
restricted so long as their total is no greater than 40% by mass,
but the proportion of bicyclic or greater saturated components
among the saturated components is preferably no greater than 20% by
mass, more preferably no greater than 15% by mass and even more
preferably no greater than 11% by mass. Also, the proportion of
bicyclic or greater saturated components among the saturated
components is preferably at least 0.5% by mass, more preferably at
least 0.8% by mass and even more preferably at least 1% by mass.
The proportion of monocyclic saturated components in the saturated
components may be 0% by mass, but it is preferably 0.1% by mass or
greater, and preferably no greater than 20% by mass, more
preferably no greater than 10% by mass, even more preferably no
greater than 5% by mass and most preferably no greater than 3% by
mass.
The ratio (M.sub.A/M.sub.B) between the mass of monocyclic
saturated components (M.sub.A) and the mass of bicyclic or greater
saturated components (M.sub.B) of the cyclic saturated components
in the lubricating base oil of the invention is preferably no
greater than 20, more preferably no greater than 3, even more
preferably no greater than 2, yet more preferably no greater than 1
and most preferably no greater than 0.5. M.sub.A/M.sub.B may be
zero, but it is preferably 0.01 or greater and more preferably 0.05
or greater. If M.sub.A/M.sub.B satisfies this condition, it will be
possible to achieve even higher levels for both the
viscosity-temperature characteristic and heat and oxidation
stability.
The saturated component content according to the invention is the
value measured based on ASTM D 2007-93 (units: % by mass).
The proportions of cyclic saturated components, monocyclic
saturated components, bicyclic or greater saturated components and
acyclic saturated components among the saturated components,
according to the invention, are the naphthene portion (monocyclic
to hexacyclic naphthenes, units: % by mass) and alkane portion
(units: % by mass), each measured based on ASTM D 2786-91.
The straight-chain paraffin content of the lubricating base oil
according to the invention is that obtained by subjecting the
saturated component portion that has been separated and
fractionated by the method described in ASTM D 2007-93 mentioned
above, to gas chromatography under the conditions described below,
in order to identify and quantify the straight-chain paraffin
content of the saturated component, and expressing the measured
value with respect to the total mass of the lubricating base oil.
For identification and quantitation, a C5-50 straight-chain
paraffin mixture sample is used as the standard sample, and the
straight-chain paraffin content among the saturated components is
determined as the proportion of the total of the peak areas
corresponding to each straight-chain paraffin, with respect to the
total peak area of the chromatogram (subtracting the peak area for
the diluent).
(Gas Chromatography Conditions)
Column: Liquid phase nonpolar column (length: 25 mm, inner
diameter: 0.3 mm.phi., liquid phase film thickness: 0.1 .mu.m)
Temperature elevating conditions: 50.degree. C.-400.degree. C.
(temperature-elevating rate: 10.degree. C./min)
Carrier gas: Helium (linear speed: 40 cm/min)
Split ratio: 90/1
Sample injection rate: 0.5 .mu.L (injection rate of sample diluted
20-fold with carbon disulfide)
The proportion of branched paraffins in the lubricating base oil is
the difference between the acyclic saturated component content
among the saturated components and the straight-chain paraffin
content among the saturated components, and it is a value expressed
with respect to the total mass of the lubricating base oil.
Separation of the saturated components or composition analysis of
the cyclic saturated components and acyclic saturated components
may be accomplished using similar methods that give comparable
results. For example, in addition to the methods described above,
there may be mentioned the method of ASTM D 2425-93, the method of
ASTM D 2549-91, high performance liquid chromatography (HPLC)
methods and modified forms of these methods.
The aromatic content of the lubricating base oil of the invention
is not particularly restricted so long as the saturated component
content, the proportion of cyclic saturated components among the
saturated components, the viscosity index, the aniline point and
the .epsilon.-methylene proportion satisfy the aforementioned
conditions, but it is preferably no greater than 5% by mass, more
preferably no greater than 4% by mass and even more preferably no
greater than 3% by mass, and also preferably 0.1% by mass or
greater, more preferably 0.5% by mass or greater, even more
preferably 1% by mass or greater and most preferably 1.5% by mass
or greater, based on the total mass of the lubricating base oil. If
the aromatic content exceeds the aforementioned upper limit, the
viscosity-temperature characteristic, heat and oxidation stability
and frictional properties, as well as the resistance to
volatilization and low temperature viscosity characteristic, will
tend to be reduced, and the efficacy of additives will be reduced
when additives are included in the lubricating base oil. The
lubricating base oil of the invention may be free of aromatic
components, but an aromatic content above the aforementioned lower
limit can further increase the solubility of additives.
The aromatic content for the invention is the value measured
according to ASTM D 2007-93. The aromatic components normally
include alkylbenzenes and alkylnaphthalenes, as well as anthracene,
phenanthrene and their alkylated forms, and compounds with four or
more condensed benzene rings, aromatic compounds with heteroatoms
such as pyridines, quinolines, phenols and naphthols, and the
like.
The viscosity index of the lubricating base oil of the invention is
at least 110 as mentioned above, but it is preferably 120 or
greater, more preferably 130 or greater, even more preferably 135
or greater and most preferably 138 or greater. If the viscosity
index is less than 110, the viscosity-temperature characteristic
may be insufficient, while the heat and oxidation stability and
resistance to volatilization may be reduced. The "viscosity index"
for the invention is the viscosity index measured according to JIS
K 2283-1993.
The aniline point (AP (.degree. C.)) of the lubricating base oil of
the invention is 106.degree. C. or higher as mentioned above, but
it is preferably 110.degree. C. or higher, more preferably
115.degree. C. or higher and even more preferably 118.degree. C. or
higher. If the aniline point is below the aforementioned lower
limit, the viscosity-temperature characteristic, heat and oxidation
stability, resistance to volatilization and low temperature
viscosity property may be reduced, and the efficacy of additives
may be lower when additives are included in the lubricating base
oil. The aniline point for the invention is the aniline point
measured according to JIS K 2256-1985.
The .epsilon.-methylene proportion of the total constituent carbons
of the lubricating base oil of the invention is 14-20% as mentioned
above, but it is preferably 14.5-19%, more preferably 15-18% and
most preferably 15-17%. If the .epsilon.-methylene proportion is
less than 14% the viscosity-temperature characteristic and heat and
oxidation stability may be reduced, while if it exceeds 20% the low
temperature viscosity property will tend to be lower, and
significantly lower at above 25%. As a different aspect of the
invention, an .epsilon.-methylene proportion of at least 20% and no
greater than 25%, and preferably 20.5-24% will allow a viscosity
index of between 140 and 160 and preferably 142-150 to be achieved,
in order to obtain a lubricating base oil with a satisfactory low
temperature viscosity property and sufficient heat and oxidation
stability. This type of lubricating base oil can exhibit, for
example, a -35.degree. C. CCS viscosity of less than 3000 mPas,
preferably 2200-2900 mPas and even more preferably 2300-2800 mPas,
and a lubricating oil composition employing such a lubricating base
oil can exhibit a -40.degree. C. MRV viscosity of 60,000 mPas or
lower and preferably 40,000 mPas or lower.
The .epsilon.-methylene proportion of the total constituent carbons
of the lubricating base oil of the invention is the proportion of
the total integrated intensity attributable to CH.sub.2 chains with
respect to the total carbon integrated intensity as measured by
.sup.13C-NMR, although another method may be used if it gives
comparable results. According to the invention, .sup.13C-NMR
measurement is conducted using a sample diluted by addition of 3 g
of heavy chloroform to 0.5 g of the sample, with a measuring
temperature of room temperature and a resonance frequency of 100
MHz. The measuring method used was gated coupling.
This method of analysis yields results for:
(a) the total integrated intensity at a chemical shift of about
10-50 ppm (total integrated intensity attributable to total
constituent carbons), and
(b) the total integrated intensity at a chemical shift of 29.7-30.0
ppm (total integrated intensity attributable to
.epsilon.-methylene),
and the proportion of (b) (%) with respect to (a) as 100% is
calculated from the results. The proportion of (b) represents the
.epsilon.-methylene proportion with respect to the total
constituent carbons in the lubricating base oil.
The .epsilon.-methylene proportion represents the proportion of
carbon atoms with a prescribed chemical shift (.epsilon.)
attributable to carbon atoms on the main chain other than the 4
carbon atoms (.alpha.-carbon, .beta.-carbon, .gamma.-carbon,
.delta.-carbon) from the main chain molecular end and branched ends
that have prescribed chemical shifts (.alpha., .beta., .gamma.,
.delta.) in NMR. Assuming equivalent molecular weight (or average
molecular weight) of the lubricating base oil, a large
.epsilon.-methylene proportion corresponds to few branches, or to a
long CH.sub.2 chain length with no branches on the main chain,
while a low .epsilon.-methylene proportion corresponds to many
branches, or a short CH.sub.2 chain length with no branches on the
main chain.
The tertiary carbon proportion of the total constituent carbons in
the lubricating base oil of the invention is not particularly
restricted but is preferably 1-15%, more preferably 5-12% and even
more preferably 6-10%. A tertiary carbon proportion within the
aforementioned range will make it possible to obtain a lubricating
base oil with an excellent viscosity-temperature characteristic and
high heat and oxidation stability. According to the invention, if
the tertiary carbon proportion of the total constituent carbons in
the lubricating base oil is 5-8% and preferably 6-7%, the obtained
lubricating oil composition will have a higher viscosity index, a
lower -35.degree. C. CCS viscosity and a smaller NOACK evaporation,
whereas if the tertiary carbon proportion is 8-10% and preferably
9-10%, it will have a lower -40.degree. C. MRV viscosity and a
superior effect of preventing acid number increase in the presence
of NOx. The tertiary carbon proportion is the proportion of carbon
atoms of >CH-- groups among the total constituent carbons, i.e.
the proportion of carbon atoms in branches or in naphthenes.
Although, as mentioned above, the tertiary carbon proportion is the
total integrated intensity attributable to tertiary carbons with
respect to the total integrated intensity for all carbons as
measured by .sup.13C-NMR, another method may be used if it gives
similar results.
The aforementioned method of analysis yields results for:
(a) the total integrated intensity at a chemical shift of about
10-50 ppm (total integrated intensity attributable to total
constituent carbons), and
(c) the total integrated intensity at chemical shifts of 27.9-28.1
ppm, 28.4-28.6 ppm, 32.6-33.2 ppm, 34.4-34.6 ppm, 37.4-37.6 ppm,
38.8-39.1 ppm and 40.4-40.6 ppm (total integrated intensity
attributable to tertiary carbons bonded to methyl, ethyl and other
branching groups and naphthenic tertiary carbons),
and the proportion of (c) (%) with respect to (a) as 100% is
calculated from the results. The proportion of (c) represents the
tertiary carbon proportion with respect to the total constituent
carbons in the lubricating base oil.
The proportion of carbons in terminal methyl groups (--CH.sub.3)
among the total constituent carbons in the lubricating base oil of
the invention is not particularly restricted but is preferably
10-20%, more preferably 12-18% and even more preferably 14-16%. A
proportion of carbons in terminal methyl groups within the
aforementioned range will make it possible to obtain a lubricating
base oil with an excellent viscosity-temperature characteristic and
heat and oxidation stability.
Although, as mentioned above, the proportion of carbons in terminal
methyl groups is the proportion of total integrated intensity
attributable to carbons in terminal methyl groups with respect to
the total integrated intensity for all carbons as measured by
.sup.13C-NMR, another method may be used if it gives similar
results.
This method of analysis yields results for:
(a) the total integrated intensity at a chemical shift of about
10-50 ppm (total integrated intensity attributable to total
constituent carbons), and
(d) the total integrated intensity at chemical shifts of 10.7-11.6
ppm, 13.8-14.7 ppm, 19.2-20.1 ppm and 22.5-22.8 ppm (total
integrated intensity attributable to carbon atoms of terminal
methyl groups (--CH.sub.3)),
and the proportion of (d) (%) with respect to (a) as 100% is
calculated from the results. The proportion of (d) represents the
proportion of terminal methyl groups with respect to the total
constituent carbons in the lubricating base oil.
The other properties and components of the lubricating base oil of
the invention are not particularly restricted so long as the
saturated component content, the proportion of cyclic saturated
components among the saturated components, the viscosity index, the
aniline point and the .epsilon.-methylene proportion satisfy the
aforementioned conditions, but the carbon distribution in the
lubricating base oil of the invention is preferably a mean number
of carbons of 20-35, more preferably 25-35 and even more preferably
28-30.
The % C.sub.P of the lubricating base oil of the invention is not
particularly restricted but is preferably 80 or greater, more
preferably 82-99, even more preferably 85-98 and yet more
preferably 90-97. If the % C.sub.P of the lubricating base oil is
less than 80, the viscosity-temperature characteristic, heat and
oxidation stability and frictional properties will tend to be
reduced, and the efficacy of additives will tend to be reduced when
additives are included in the lubricating base oil. If the %
C.sub.P of the lubricating base oil exceeds 99, the solubility of
additives will tend to be lower.
The % C.sub.N of the lubricating base oil of the invention is not
particularly restricted but is preferably no greater than 12, more
preferably 1-12 and even more preferably 3-10. If the % C.sub.N of
the lubricating base oil is greater than 12, the
viscosity-temperature characteristic, heat and oxidation stability
and frictional properties will tend to be reduced. If % C.sub.N is
less than 1, the solubility of additives will tend to be lower.
The % C.sub.A of the lubricating base oil of the invention is not
particularly restricted but is preferably no greater than 0.7, more
preferably no greater than 0.6 and even more preferably no greater
than 0.1-0.5. If the % C.sub.A of the lubricating base oil is
greater than 0.7, the viscosity-temperature characteristic, heat
and oxidation stability and frictional properties will tend to be
reduced. The % C.sub.A of the lubricating base oil of the invention
may be zero, but a % C.sub.A of 0.1 or greater can further increase
the solubility of additives.
There are no particular restrictions on the ratio of % C.sub.P and
% C.sub.N in the lubricating base oil of the invention, but %
C.sub.P/% C.sub.N is preferably at least 7, more preferably at
least 7.5 and even more preferably at least 8. If the % C.sub.P/%
C.sub.N is less than 7, the viscosity-temperature characteristic,
heat and oxidation stability and frictional properties will tend to
be reduced, and the efficacy of additives will tend to be reduced
when additives are included in the lubricating base oil. Also, %
C.sub.P/% C.sub.N is preferably no greater than 200, more
preferably no greater than 100, even more preferably no greater
than 50 and most preferably no greater than 25. A % C.sub.P/%
C.sub.N ratio of 200 or smaller can further increase the solubility
of additives.
The values of % C.sub.P, % C.sub.N and % C.sub.A according to the
invention are, respectively, the percentage of the number of
paraffin carbon atoms with respect to the total number of carbon
atoms, the percentage of naphthene carbon atoms with respect to the
total number of carbon atoms and the percentage of aromatic carbon
atoms with respect to the total number of carbon atoms, as
determined by the method of ASTM D 3238-85 (n-d-M ring analysis).
That is, the preferred ranges for % C.sub.P, % C.sub.N and %
C.sub.A are based on values determined by this method, and for
example, % C.sub.N determined by the method may be a value
exceeding zero even when the lubricating base oil contains no
naphthene components.
The sulfur content of the lubricating base oil of the invention
depends on the sulfur content of the stock oil. For example, when
using a stock oil containing essentially no sulfur, such as a
synthetic wax component obtained by Fischer-Tropsch reaction, it is
possible to obtain a lubricating base oil containing essentially no
sulfur. Or, when using a stock oil that contains sulfur, such as
slack wax obtained by a lubricating base oil refining process or a
microwax obtained by a wax refining process, the sulfur content of
the obtained lubricating base oil will usually be 100 ppm by mass
or greater. From the viewpoint of further improving the heat and
oxidation stability and lowering the sulfur content, the sulfur
content of the lubricating base oil of the invention is preferably
no greater than 100 ppm by mass, more preferably no greater than 50
ppm by mass, even more preferably no greater than 10 ppm by mass
and most preferably no greater than 5 ppm by mass.
From the viewpoint of cost reduction, the stock oil used is
preferably slack wax, in which case the sulfur content of the
obtained lubricating base oil is preferably no greater than 50 ppm
by mass and more preferably no greater than 10 ppm by mass. The
sulfur content of the invention is the sulfur content measured
according to JIS K 2541-1996.
The nitrogen content of the lubricating base oil of the invention
is not particularly restricted, but it is preferably no greater
than 5 ppm by mass, more preferably no greater than 3 ppm by mass
and even more preferably no greater than 1 ppm by mass. If the
nitrogen content is greater than 5 ppm by mass, the heat and
oxidation stability will tend to be reduced. The nitrogen content
of the invention is the nitrogen content measured according to JIS
K 2609-1990.
There are no particular restrictions on the 100.degree. C.
kinematic viscosity of the lubricating base oil of the invention,
but it is generally 1-10 mm.sup.2/s, preferably 3.5-6 mm.sup.2/s,
more preferably 3.7-4.5 mm.sup.2/s and even more preferably 3.9-4.2
mm.sup.2/s. If the 100.degree. C. kinematic viscosity of the
lubricating base oil is less than 3.5 mm.sup.2/s the evaporation
loss will tend to be increased, while if it is greater than 6
mm.sup.2/s the low temperature viscosity property at -40.degree. C.
will tend to be significantly impaired.
There are also no particular restrictions on the 40.degree. C.
kinematic viscosity of the lubricating base oil of the invention,
but it is generally 5-100 mm.sup.2/s, preferably 12-32 mm.sup.2/s,
more preferably 13-19 mm.sup.2/s and even more preferably 15-17.5
mm.sup.2/s. If the 40.degree. C. kinematic viscosity of the
lubricating base oil is less than 12 mm.sup.2/s the evaporation
loss will tend to be increased, while if it is greater than 32
mm.sup.2/s the low temperature viscosity property at -40.degree. C.
will tend to be impaired.
There are, in addition, no particular restrictions on the solid
point of the lubricating base oil of the invention, but it is
preferably no higher than -20.degree. C., more preferably no higher
than -25.degree. C. and even more preferably no higher than
-28.degree. C. Under temperature conditions of about -30.degree. C.
it is possible to achieve sufficient low-temperature
characteristics even when the solid point of the lubricating base
oil exceeds -25.degree. C., but in order to obtain a lubricating
oil with excellent low temperature viscosity properties (CCS
viscosity, MRV viscosity, BF viscosity) at below -35.degree. C. and
especially a lubricating oil with significant improvement in the
MRV viscosity at -40.degree. C., it is important for the solid
point to be no higher than -20.degree. C. and especially no higher
than -25.degree. C. Also, although the low temperature performance
can be improved by lowering the solid point of the lubricating base
oil, from the viewpoint of a lower viscosity index and of economy,
the solid point is preferably -45.degree. C. or higher, more
preferably -40.degree. C. or higher and even more preferably
-35.degree. C. or higher. According to the invention, the solid
point of the lubricating base oil is most preferably -35 to
-25.degree. C. to obtain a lubricating base oil with a high level
of both high viscosity index and low-temperature characteristics,
as well as excellent economy. A lubricating base oil with a solid
point of no higher than -20.degree. C. can be obtained by dewaxing
treatment such as the aforementioned solvent dewaxing process or
catalytic dewaxing process, but any dewaxing treatment method may
be employed so long as it can yield a dewaxed lubricating base oil
with a solid point of no higher than -20.degree. C.
The solid point according to the invention is a temperature
1.degree. C. below the minimum temperature at which flow of the
sample is observed, as measured with the pour point measuring
interval (2.5.degree. C.) according to JIS K 2269-1987 (JIS pour
point) set to 1.degree. C. The JIS pour point gives results for an
interval of 2.5.degree. C., but from the viewpoint of measuring
error and reproducibility, this method is not suitable for the
invention which requires strict control of the critical point for
the low-temperature characteristic.
The -35.degree. C. CCS viscosity of the lubricating base oil of the
invention is preferably no greater than 2800 mPas, more preferably
no greater than 2200 mPas and even more preferably no greater than
2000 mPas. The -35.degree. C. CCS viscosity for the invention is
the viscosity measured according to JIS K2010-1993.
A lubricating base oil of the invention may be used in a
lubricating oil composition of the invention to obtain a
-40.degree. C. MRV viscosity of preferably no greater than 30,000
mPas, more preferably no greater than 20,000 mPas, even more
preferably no greater than 15,000 mPas, yet more preferably no
greater than 13,000 mPas, even yet more preferably no greater than
12,000 mPas, especially preferably no greater than 10,000 mPas and
most preferably no greater than 8000 mPas, and also with a yield
stress of 0 Pa (no yield stress). The -40.degree. C. MRV viscosity
and yield stress for the invention are the viscosity and yield
stress as measured according to ASTM D 4684.
A lubricating base oil of the invention may be used in a
lubricating oil composition of the invention to obtain a
-40.degree. C. BF viscosity of preferably no greater than 20,000
mPas, more preferably no greater than 15,000 mPas, even more
preferably no greater than 10,000 mPas and most preferably no
greater than 8000 mPas. The -40.degree. C. BF viscosity for the
invention is the viscosity as measured according to
JPI-5S-26-99.
The lubricating base oil of the invention preferably satisfies the
conditions represented by the following inequality (1).
1.435.ltoreq.n.sub.20-0.002.times.kv100.ltoreq.1.453 (1) [wherein
n.sub.20 represents the refractive index of the lubricating base
oil at 20.degree. C., and kv100 represents the kinematic viscosity
(mm.sup.2/s) of the lubricating base oil at 100.degree. C.]
Also, n.sub.20-0.002.times.kv100 for the lubricating base oil of
the invention is preferably 1.435-1.450, more preferably
1.440-1.449, even more preferably 1.442-1.448 and most preferably
1.444-1.447. For production of a lubricating base oil having such
properties, the stock oil introduced into the hydrocracking and/or
hydroisomerization step is preferably one composed mainly of the
aforementioned synthetic wax and/or slack wax, and more preferably
a starting material composed mainly of the aforementioned synthetic
wax and/or slack wax A. In this case, the proportion of branched
paraffins in the lubricating base oil is preferably 80-99% by mass,
but if the lubricating base oil is obtained using the
aforementioned synthetic wax as the stock oil, the proportion of
branched paraffins in the lubricating base oil is more preferably
95-99% by mass and even more preferably 97-99% by mass, while if
the lubricating base oil is obtained using the aforementioned slack
wax A as the stock oil, the proportion of branched paraffins is
more preferably 82-98% by mass and even more preferably 90-95% by
mass.
When the lubricating base oil of the invention is a lubricating
base oil with a saturated component content of 90% by mass or
greater and a proportion of cyclic saturated components of 5-40% by
mass and preferably 10-25% by mass among the saturated components,
n.sub.20-0.002.times.kv100 may be 1.435-1.453, preferably
1.440-1.452, more preferably 1.442-1.451 and even more preferably
1.444-1.450. For production of a lubricating base oil having such
properties, the starting material introduced into the hydrocracking
and/or hydroisomerization step is preferably one composed mainly of
the aforementioned synthetic wax and/or slack wax, and more
preferably a starting material composed mainly of slack wax B. In
this case, the proportion of branched paraffins in the lubricating
base oil is more preferably 54-99% by mass, even more preferably
58-95% by mass, yet more preferably 70-92% by mass and most
preferably 80-90% by mass.
If n.sub.20-0.002.times.kv100 is within the aforementioned range,
it is possible to achieve even higher levels for both the
viscosity-temperature characteristic and heat and oxidation
stability, and when additives are included in the lubricating base
oil, it can exhibit an even higher level of function for the
additives while maintaining satisfactorily stable dissolution of
the additives in the lubricating base oil. Limiting
n.sub.20-0.002.times.kv100 to the aforementioned range can also
improve the frictional properties of the lubricating base oil
itself, resulting in an enhanced friction reducing effect and thus
increased energy savings.
If n.sub.20-0.002.times.kv100 exceeds the aforementioned upper
limit, the viscosity-temperature characteristic, heat and oxidation
stability and frictional properties will tend to be insufficient,
and the efficacy of additives will tend to be reduced when
additives are included in the lubricating base oil. If
n.sub.20-0.002.times.kv100 is below the aforementioned lower limit,
the solubility of additives will be insufficient when additives are
included in the lubricating base oil, and the effective amount of
additives kept dissolved in the lubricating base oil will be
reduced, thus tending to prevent the additives from effectively
exhibiting their functions.
In order to satisfy the above inequality, the 20.degree. C.
refractive index of the lubricating base oil of the invention is
preferably 1.450-1.465, more preferably 1.452-1.463 and even more
preferably 1.453-1.462. The 20.degree. C. refractive index
(n.sub.20) for the invention is the refractive index measured at
20.degree. C. according to ASTM D1218-92. The 100.degree. C.
kinematic viscosity (kv100) for the invention is the kinematic
viscosity measured at 100.degree. C. according to JIS K
2283-1993.
The pour point of the lubricating base oil composition of the
invention is preferably no higher than -20.degree. C., more
preferably no higher than -22.5.degree. C., even more preferably no
higher than -25.degree. C., yet more preferably no higher than
-27.5.degree. C. and most preferably no higher than -30.degree. C.
If the pour point is above the aforementioned upper limit, the low
temperature viscosity property of the lubricating base oil and
lubricating oil composition at below -35.degree. C. will tend to be
impaired. The pour point for the invention is the pour point
measured according to JIS K 2269-1987.
The 15.degree. C. density (.rho..sub.15, units: g/cm.sup.3) of the
lubricating base oil of the invention is preferably no greater than
0.835 g/cm.sup.3, more preferably no greater than 0.830 g/cm.sup.3
and even more preferably no greater than 0.825 g/cm.sup.3, and also
preferably at least 0.810 g/cm.sup.3. The 15.degree. C. density for
the invention is the density measured at 15.degree. C. according to
JIS K 2249-1995.
The NOACK evaporation of the lubricating base oil of the invention
is not particularly restricted, but it is preferably no greater
than 20% by mass, more preferably no greater than 16% by mass, even
more preferably no greater than 15% by mass, yet more preferably no
greater than 14% by mass and most preferably no greater than 12% by
mass, and also preferably 6% by mass or greater, more preferably 8%
by mass or greater and even more preferably 10% by mass or greater.
If the NOACK evaporation is below the aforementioned lower limit,
it will tend to be difficult to achieve improvement in the low
temperature viscosity property. The NOACK evaporation is preferably
not above the aforementioned upper limit because evaporation loss
of the lubricating oil will become considerable and catalyst
poisoning will be accelerated, when the lubricating base oil is
used as an internal combustion engine lubricating oil. The NOACK
evaporation for the invention is the evaporation loss measured
according to ASTM D 5800-95.
The iodine number of the lubricating base oil of the invention is
preferably no greater than 2.5, more preferably no greater than
1.5, even more preferably no greater than 1 and most preferably no
greater than 0.8, and while it may be less than 0.01, it is
preferably 0.01 or greater, more preferably 0.1 or greater and even
more preferably 0.5 or greater from the standpoint of economy and
of exhibiting a substantial effect. The heat and oxidation
stability can be drastically improved if the iodine number of the
lubricating base oil is 2.5 or smaller. The "iodine number" for the
invention is the iodine number measured according to the indicator
titration method described in JIS K 0070, "Chemical Product Acid
Number, Saponification Value, Iodine Number, Hydroxyl Value and
Unsaponification Value".
The distillation property of the lubricating base oil of the
invention is based on gas chromatography distillation, and the
initial boiling point (IBP) is preferably 300-380.degree. C., more
preferably 320-370.degree. C. and even more preferably
330-360.degree. C. The 10% distillation temperature (T10) is
preferably 340-420.degree. C., more preferably 350-410.degree. C.
and even more preferably 360-400.degree. C. The 50% distillation
temperature (T50) is preferably 380-460.degree. C., more preferably
390-450.degree. C. and even more preferably 400-460.degree. C. The
90% distillation temperature (T90) is preferably 440-500.degree.
C., more preferably 450-490.degree. C. and even more preferably
460-480.degree. C. The end point (FBP) is preferably
460-540.degree. C., more preferably 470-530.degree. C. and even
more preferably 480-520.degree. C. T90-T10 is preferably
50-100.degree. C., more preferably 60-95.degree. C. and even more
preferably 80-90.degree. C. FBP-IBP is preferably 100-250.degree.
C., more preferably 120-180.degree. C. and even more preferably
130-160.degree. C. T10-IBP is preferably 10-70.degree. C., more
preferably 15-60.degree. C. and even more preferably 20-50.degree.
C. FBP-T90 is preferably 10-50.degree. C., more preferably
20-40.degree. C. and even more preferably 25-35.degree. C. If IBP,
T10, T50, T90, FBP, T90-T10, FBP-IBP, T10-IBP and FBP-T90 are
established within the aforementioned preferred ranges it will be
possible to achieve further improvement in the low temperature
viscosity and further reduction in evaporation loss. If each
distillation ranges of T90-T10, FBP-IBP, T10-IBP and FBP-T90 that
are too narrow, the lubricating base oil yield will be lower,
therefore it will be uneconomical. For the purpose of the
invention, IBP, T10, T50, T90 and FBP are the distillated
temperature measured according to ASTM D 2887-97.
The residual metal content of the lubricating base oil of the
invention is based on the catalyst and the metals in the starting
materials that are unavoidable contaminants in the production
process, and it is preferred for such residual metals to be
thoroughly removed. For example, the Al, Mo and Ni contents are
preferably each 1 ppm by mass or less. If the contents of these
metals exceed the aforementioned upper limit, the functions of
additives included in the lubricating base oil will tend to be
inhibited.
The residual metal content for the invention is the metal content
as measured according to JPI-5S-38-2003.
The lubricating base oil of the invention can exhibit excellent
heat and oxidation stability if the saturated component content,
the proportion of cyclic saturated components among the saturated
components, the viscosity index, the aniline point and the
.epsilon.-methylene proportion satisfy the aforementioned
conditions, but in addition the RBOT life is preferably 350 min or
greater, more preferably 370 min or greater and even more
preferably 380 min or greater. If the RBOT life is shorter than
this range, the viscosity-temperature characteristic and heat and
oxidation stability of the lubricating base oil will tend to be
reduced, and the efficacy of additives will tend to be reduced when
additives are included in the lubricating base oil.
The RBOT life for the invention is the RBOT value as measured
according to JIS K 2514-1996, for a composition obtained by adding
a phenolic antioxidant (2,6-di-tert-butyl-p-cresol; DBPC) at 0.2%
by mass to the lubricating base oil.
The lubricating base oil of the invention may be used alone as a
lubricating oil, but alternatively the lubricating base oil of the
invention may be used as a lubricating oil composition, in
combination with one or more other base oils and/or additives.
When the lubricating oil composition of the invention comprises a
lubricating base oil of the invention and another base oil, the
proportion of the lubricating base oil of the invention in the
blended base oil is preferably at least 30% by mass, more
preferably at least 50% by mass and even more preferably at least
70% by mass.
There are no particular restrictions on other base oils to be used
in combination with the lubricating base oil of the invention, and
as examples of mineral oil base oils there may be mentioned solvent
refined mineral oils, hydrocracked mineral oils, hydrorefined
mineral oils and solvent dewaxed base oils with 100.degree. C.
dynamic viscosities of 1-100 mm.sup.2/s.
As synthetic base oils there may be mentioned poly .alpha.-olefins
and their hydrogenated products, isobutene oligomers and their
hydrogenated products, isoparaffins, alkylbenzenes,
alkylnaphthalenes, diesters (ditridecyl glutarate, di-2-ethylhexyl
adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl
sebacate and the like), polyol esters (trimethylolpropane
caprylate, trimethylolpropane pelargonate, pentaerythritol 2-ethyl
hexanoate, pentaerythritol pelargonate and the like),
polyoxyalkylene glycols, dialkyldiphenyl ethers, polyphenyl ethers,
and the like, among which poly .alpha.-olefins are preferred. As
typical poly .alpha.-olefins there may be mentioned C2-32 and
preferably C6-16 .alpha.-olefin oligomers or co-oligomers (1-octene
oligomers, decene oligomers, ethylene-propylene co-oligomers and
the like), and their hydrogenated products.
There are no particular restrictions on the method of preparing the
poly .alpha.-olefins, and for example, there may be mentioned a
method of polymerizing an .alpha.-olefin in the presence of a
polymerization catalyst such as a Friedel-Crafts catalyst
comprising a complex of aluminum trichloride or boron trifluoride
with water, an alcohol (ethanol, propanol, butanol or the like), a
carboxylic acid or an ester.
The lubricating oil composition of the invention may further
contain additives. As additives to be included in the lubricating
oil composition of the invention there may be used any additives
conventionally employed in the field of lubricating oils, without
any particular restrictions. As such lubricating oil additives
there may be mentioned, specifically, antioxidants, ashless
dispersants, metallic detergents, extreme-pressure agents,
anti-wear agents, viscosity index improvers, pour point
depressants, friction modifiers, oiliness agents, corrosion
inhibitors, rust inhibitors, demulsifiers, metal deactivating
agents, seal swelling agents, antifoaming agents, coloring agents
and the like. These additives may be used alone or in combinations
of two or more.
The lubricating oil composition of the invention preferably
contains a pour point depressant and/or viscosity index improver
among the aforementioned additives, from the viewpoint of notably
improving the -40.degree. C. BF viscosity or MRV viscosity. The
pour point of a lubricating oil composition containing a pour point
depressant and/or viscosity index improver is preferably -60 to
-35.degree. C. and more preferably -50 to -40.degree. C.
The lubricating oil composition of the invention preferably also
contains a viscosity index improver from the viewpoint of achieving
further improvement in the viscosity-temperature characteristic As
specific examples of viscosity index improvers there may be
mentioned non-dispersed or dispersed polymethacrylates, dispersed
ethylene-.alpha.-olefin copolymers or their hydrogenated products,
polybutylene or its hydrogenated products, styrene-diene
hydrogenation copolymer, styrene-maleic anhydride copolymer and
polyalkylstyrenes, among which there are preferred non-dispersed
viscosity index improvers and/or dispersed viscosity index
improvers with weight-average molecular weights of
10,000-1,000,000, preferably 100,000-900,000, more preferably
150,000-500,000 and even more preferably 180,000-400,000. There are
no particular restrictions on the PSSI (Permanent Shear Stability
Index) of the viscosity index improver, but it is preferably 1-100
and more preferably 10-90, while for increased fuel efficiency it
is even more preferably 50 or greater and most preferably 55 or
greater. In order to achieve high levels of both shear stability
and fuel efficiency, it is preferably 25-50 and even more
preferably 30-45. The PSSI referred to here is the Permanent Shear
Stability Index of the polymer as calculated based on ASTM D
6278-02 (Test Method for Shear Stability of Polymer Containing
Fluid Using a European Diesel Injector Apparatus), according to
ASTM D 6022-01 (Standard Practice for Calculation of Permanent
Shear Stability Index).
Polymethacrylate-based viscosity index improvers are preferred
among the viscosity index improvers mentioned above from the
standpoint of achieving a more excellent low-temperature flow
property, and dispersed polymethacrylate-based viscosity index
improvers are especially preferred from the standpoint of
dispersibility of oxidative degradation products.
The viscosity index improver content in the lubricating oil
composition of the invention is preferably 0.1-15% by mass and more
preferably 0.5-5% by mass based on the total mass of the
composition. If the viscosity index improver content is less than
0.1% by mass, the improving effect on the viscosity-temperature
characteristic by the addition will tend to be insufficient, while
if it is greater than 15% by mass the heat and oxidation stability
will tend to be reduced.
There are also no particular restrictions on the 100.degree. C.
kinematic viscosity of the lubricating oil composition of the
invention, but it is preferably 4.5-21.9 mm.sup.2/s, more
preferably 5-16.3 mm.sup.2/s, even more preferably 5.5-12.5
mm.sup.2/s and most preferably 5.5-9.3 mm.sup.2/s. The viscosity
index is also not particularly restricted but is preferably 160 or
greater, more preferably 180 or greater, even more preferably 200
or greater, yet more preferably 210 or greater and most preferably
220 or greater. By increasing the viscosity index of the
lubricating oil composition, it is possible to obtain a lubricating
oil composition with an excellent viscosity index from low
temperatures of below -35.degree. C. to high temperatures, and to
obtain a lubricating oil, and especially an engine oil or a drive
transmission device lubricating oil, with even higher energy
savings (fuel efficiency). According to the invention, it is
possible to obtain a 0W-10 or 0W-20 fuel efficient engine oil with
a 100.degree. C. kinematic viscosity of 5-9 mm.sup.2/s, or a fuel
efficient drive transmission device lubricating oil with a
100.degree. C. kinematic viscosity of 5-6 mm.sup.2/s.
The lubricating base oil and lubricating oil composition of the
invention having the structure described above exhibit excellent
viscosity-temperature characteristics and heat and oxidation
stability, as well as improved frictional properties of the
lubricating base oil itself, and can provide both an improved
friction reducing effect and enhanced energy savings. The
lubricating oil composition of the invention allows additives to
exhibit a higher level of function (heat and oxidation stability
improving effect due to antioxidants, friction reducing effect due
to friction modifiers, wear resistance improvement effect due to
anti-wear agent, etc.) when additives are included in the
lubricating base oil of the invention. The lubricating base oil and
lubricating oil composition of the invention are therefore suitable
for use in a variety of lubricating oil fields. As specific uses
for the lubricating base oil and lubricating oil composition of the
invention, there may be mentioned lubricating oils (internal
combustion engine lubricating oils) used in internal combustion
engines such as passenger vehicle gasoline engines, two-wheeler
gasoline engines, diesel engines, gas engines, gas heat pump
engines, marine engines, electric power engines and the like,
lubricating oils (drive transmission device oils) used in drive
transmission devices such as automatic transmissions, manual
transmissions, continuously variable transmissions, final reduction
gears and the like, hydraulic oils used in hydraulic power units
such as dampers, construction equipment and the like, as well as
compressor oils, turbine oils, industrial gear oils, refrigerator
oils, rust preventing oils, heating medium oils, gas holder seal
oils, bearing oils, paper machine oils, machine tool oils, sliding
guide surface oils, electrical insulation oils, cutting oils, press
oils, rolling oils, heat treatment oils and the like, and using a
lubricating base oil or lubricating oil composition of the
invention for such uses can improve the properties of lubricating
oils including the viscosity-temperature characteristic, heat and
oxidation stability, energy savings and fuel efficiency, while
lengthening the lubricating oil life and achieving a higher level
of reduction in the environmentally detrimental substances.
EXAMPLES
The present invention will now be explained in greater detail based
on examples and comparative examples, with the understanding that
these examples are in no way limitative on the invention.
Example 1
After mixing and kneading 800 g of USY zeolite and 200 g of an
alumina binder, the mixture was shaped into a cylinder with a
diameter of 1/16 inch (approximately 1.6 mm) and a height of 6 mm.
The shaped body was calcinated at 450.degree. C. for 3 hours to
obtain a carrier. The carrier was impregnated with an aqueous
solution containing dichlorotetraamineplatinum (II) in an amount of
0.8% by mass of the carrier in terms of platinum, and then dried at
120.degree. C. for 3 hours and calcinated at 400.degree. C. for 1
hour to obtain the catalyst.
Next, 200 ml of the obtained catalyst was packed into a fixed-bed
circulating reactor, and the reactor was used for
hydrocracking/hydroisomerization of the paraffinic
hydrocarbon-containing stock oil. The stock oil used in this step
was FT wax with a paraffin content of 95% by mass and a carbon
number distribution from 20 to 80 (hereinafter referred to as
"WAX1"). The properties of WAX1 are shown in Table 1. The
conditions for the hydrocracking were a hydrogen pressure of 3 MPa,
a reaction temperature of 350.degree. C. and an LHSV of 2.0
h.sup.-1, and a cracking/isomerization product oil was obtained
comprising 30% by mass of the fraction with a boiling point of
380.degree. C. and below (cracked product) with respect to the
stock oil (30% cracking severity).
TABLE-US-00001 TABLE 1 Name of starting wax WAX1 Kinematic
viscosity at 100.degree. C. (mm.sup.2/s) 5.8 Melting point
(.degree. C.) 70 Oil content (% by mass) <1 Sulfur content (ppm
by mass) <0.2
The cracked product obtained by the hydrocracking was subjected to
vacuum distillation to obtain a lube-oil distillate with a
100.degree. C. kinematic viscosity of 4 mm.sup.2/s. The lube-oil
distillate was prepared with a methyl ethyl ketone-toluene mixed
solvent to a solvent/oil ratio of 4, and subjected to solvent
dewaxing until the solid point of the obtained solvent-dewaxed oil
fell below -25.degree. C., to obtain a lubricating base oil for
Example 1 (hereinafter referred to as "base oil 1"). The dewaxing
temperature was -25.degree. C.
Example 2
The fraction separated by vacuum distillation in the step of
refining a solvent refined base oil was subjected to solvent
extraction with furfural and then to hydrotreatment, after which
solvent dewaxing was performed with a methyl ethyl ketone-toluene
mixed solvent. The slack wax removed during the solvent dewaxing
was deoiled to obtain a wax portion (hereinafter referred to as
"WAX2") for use as a lubricating base oil starting material. The
properties of WAX2 are shown in Table 2.
TABLE-US-00002 TABLE 2 Name of starting wax WAX2 Kinematic
viscosity at 100.degree. C. (mm.sup.2/s) 6.8 Melting point
(.degree. C.) 58 Oil content (% by mass) 6.3 Sulfur content (ppm by
mass) 900
WAX2 was hydrocracked in the presence of a hydrocracking catalyst
under conditions with a hydrogen partial pressure of 5 MPa, a mean
reaction temperature of 350.degree. C. and an LHSV of 1 hr.sup.-1.
The hydrocracking catalyst used was a sulfurized catalyst
comprising 3% by mass nickel and 15% by mass molybdenum supported
on an amorphous silica-alumina carrier (silica:alumina=20:80 (mass
ratio)).
The cracked product obtained by the hydrocracking was subjected to
vacuum distillation to obtain a lube-oil distillate with a
100.degree. C. kinematic viscosity of 4 mm.sup.2/s. The lube-oil
distillate was prepared with a methyl ethyl ketone-toluene mixed
solvent to a solvent/oil ratio of 4, and subjected to solvent
dewaxing until the solid point of the obtained solvent-dewaxed oil
fell below -25.degree. C., to obtain a lubricating base oil for
Example 2 (hereinafter referred to as "base oil 2"). The dewaxing
temperature was -32.degree. C.
The properties and performance evaluation test results for the
lubricating base oils of Examples 1 and 2 are shown in Table 3.
Also, Table 4 shows the properties and performance evaluation test
results for base oils 3-6, as conventional high viscosity index
base oils for Comparative Examples 1-4.
TABLE-US-00003 TABLE 3 Example 1 Example 2 Base oil name Base oil 1
Base oil 2 Name of starting wax WAX1 WAX2 Components of base
Saturated % by mass 99.5 98.6 oil (based on Aromatic % by mass 0.4
1.3 total base oil) Polar compounds % by mass 0.1 0.1 Saturated
compound Cyclic saturated % by mass 1.3 5.0 contents (based on
Acyclic saturated % by mass 98.7 95.0 total saturated content)
EI-MS saturated Monocylic saturated % by mass 0.1 1.3 compound
analysis - Bicyclic or greater % by mass 1.2 3.7 Cyclic saturated
saturated compound contents Monocylic/bicyclic or greater 0.08 0.35
(based on total saturated (mass ratio) saturated content) Sulfur
content ppm by mass <1 <1 Nitrogen content ppm by mass <3
<3 Kinematic viscosity (40.degree. C.) mm.sup.2/s 16.7 16.3
Kinematic viscosity (100.degree. C.) kv100 mm.sup.2/s 3.9 3.9
Viscosity index 131 140 Solid point .degree. C. -28 -29
.sup.13C-NMR CH % 9.3 6.7 CH.sub.3 % 15.6 15.8 .epsilon.-Methylene
proportion % 15.8 19.6 Iodine value 0.2 0.6 Aniline point .degree.
C. 120.5 119 CCS viscosity (-35.degree. C.) mPa s 1970 1820 NOACK
evaporation (250.degree. C., 1 hour) % by mass 14.9 10.7
TABLE-US-00004 TABLE 4 Comp. Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3
Ex. 4 Base oil name Base Base Base Base oil 3 oil 4 oil 5 oil 6
Name of starting wax WAX2 WAX2 -- -- Components of Saturated % by
mass 98.5 98.4 99.7 94.7 base oil (based on Aromatic % by mass 1.3
1.4 0.3 5.3 total base oil) Polar compounds % by mass 0.2 0.2 0.0
0.0 Saturated compound Cyclic saturated % by mass 7.1 7.2 46.2 46.5
contents (based on Acyclic saturated % by mass 92.9 92.8 53.8 53.5
total saturated content) EI-MS saturated Monocyclic saturated % by
mass 3.0 3.1 -- 16.2 compound analysis - Bicyclic or greater % by
mass 4.1 4.1 26.1 30.3 Cyclic saturated saturated compound contents
Monocylic/bicyclic or greater 0.73 0.76 0.77 0.53 (based on total
saturated (mass ratio) saturated content) Sulfur content ppm by
mass <1 <1 <1 <1 Nitrogen content ppm by mass <3
<3 <3 <3 Kinematic viscosity (40.degree. C.) Mm.sup.2/s
16.3 16.1 20.0 18.7 Kinematic viscosity (100.degree. C.) kv100
Mm.sup.2/s 4.0 3.9 4.3 4.1 Viscosity index 145 144 123 121 Solid
point .degree. C. -20 -17 -20 -24 .sup.13C-NMR CH % 6.4 6.8 9.7 7.4
CH.sub.3 % 15.6 15.2 -- -- .epsilon.-Methylene proportion % 22.4
21.8 14.2 14.9 Iodine number 0.6 0.6 2.5 2.7 Aniline point .degree.
C. 119.4 119.2 115.7 112.0 CCS viscosity (-35.degree. C.) mPa s
2740 2460 3000 3500 NOACK evaporation (250.degree. C., 1 hour) % by
mass 12.4 12.0 15.5 16.1
The results in Tables 3 and 4 demonstrate that the lubricating base
oils of Examples 1 and 2 both had a superior low temperature
viscosity property (CCS viscosity at -35.degree. C.) compared to
the lubricating base oils of Comparative Examples 1-4.
Incidentally, base oil 3 and base oil 4 were lubricating base oils
produced in the same manner as base oil 2 but using WAX2 as the
starting material and performing solvent dewaxing at -20 to
-23.degree. C., and they satisfied the constituent features of the
present application claim 1 except for aforementioned
.epsilon.-methylene proportion exceeding 20% (20-24%) and exhibited
properties roughly equivalent to those of base oil 2 or base oil 1,
yet were satisfactorily superior with a high viscosity index of
140-150 and a -35.degree. C. CCS viscosity of less than 3000 mPas
(2200-2900 mPas).
Examples 3 and 4, Comparative Examples 5-8
For Examples 3 and 4 and Comparative Examples 5-8, lubricating oil
compositions listed in Tables 5 and 6 were prepared using base oils
1-6 mentioned above, dispersant type polymethacrylate with PSSI of
40 and performance additives (including antioxidants, ashless
dispersants, metallic detergents, anti-wear agents and the like).
The properties of the obtained lubricating oil compositions are
shown in Tables 5 and 6.
[NOx Absorption Test]
The lubricating oil compositions of Examples 3 and 4 and
Comparative Examples 5-8 were each subjected to a NOx absorption
test in the following manner. Following the method described in
Proceedings of JAST (the Japanese Society of Tribologists)
Tribology Conference, 1992, 10, 465, NOx-containing gas was blown
into the test oil and the time-dependent change in acid number with
forced aging was measured. The temperature for the test was
140.degree. C., and the NOx concentration of the NOx-containing gas
was 1200 ppm. The O.sub.2 concentration was 85%. The increases in
acid number after 144 hours from initial blowing in of NOx gas are
shown in Tables 5 and 6. In the tables, a smaller acid number
increase indicates a long drain oil capable of more prolonged use
even in the presence of NOx used in internal combustion
engines.
TABLE-US-00005 TABLE 5 Example 3 Example 4 Base oil components D1
100 -- [% by mass] D2 -- 100 Lubricating oil Base oil Remainder
Remainder composition components Performance additive 10 10 [% by
mass] PMA 4 4 Kinematic viscosity at 100.degree. C. [mm.sup.2/s]
8.5 8.5 Viscosity index 212 220 MRV viscosity at -40.degree. C.
[mPa s] 7400 11600 Acid number increase [mgKOH/g] 7.7 7.9
TABLE-US-00006 TABLE 6 Comp. Comp. Comp. Comp. Ex. 5 Ex. 6 Ex. 7
Ex. 8 Base oil Base oil 3 100 -- -- -- components Base oil 4 -- 100
-- -- [% by mass] Base oil 5 -- -- 100 -- Base oil 6 -- -- -- 100
Lubricating oil Base oil Re- Re- Re- Re- composition mainder
mainder mainder mainder components Performance 10 10 10 10 [% by
mass] additive PMA 4 4 4 4 Kinematic viscosity at 100.degree. C.
8.6 8.5 8.9 8.7 [mm.sup.2/s] Viscosity index 224 224 203 200 MRV
viscosity at -40.degree. C. 29000 35900 12500 25500 [mPa s] Acid
number increase [mgKOH/g] 7.8 8.2 9.4 11.5
Based on the results in Tables 5 and 6, the lubricating oil
compositions of Comparative Examples 5 and 6 exhibited sufficient
low temperature performance with a -40.degree. C. MRV viscosity of
60,000 mPas or lower, while their viscosity indexes were higher and
their acid number increases in the presence of NOx were lower than
the lubricating oil compositions of Comparative Examples 7 and 8.
However, the lubricating oil compositions of Examples 3 and 4
clearly had a superior low temperature viscosity property
(-40.degree. C. MRV viscosity) compared to the lubricating oil
compositions of Comparative Examples 5-8. Also, the lubricating oil
compositions of Examples 3 and 4 had higher viscosity indexes and
superior heat and oxidation stability compared to the lubricating
oil compositions of Comparative Examples 7 and 8.
* * * * *